In general, microphones are devices converting a voice into an electrical signal. Microphones are required to have desirable electronic and acoustic performance, reliability, and operability. Microphones have increasingly been reduced in size. Thus, there has been research into microphones using a micro-electro mechanical system (MEMS) technology.
MEMS microphones are manufactured using a semiconductor batch process. MEMS microphones have tolerance to moisture and heat, and can be miniaturized and integrated with a signal processing circuit, compared with conventional electric condenser microphones (ECMs).
Also, MEMS microphones have excellent sensitivity and low performance deviation by products, compared with conventional ECMs. Thus, MEMS microphones have been applied to various application fields, replacing ECMs.
In general, MEMS microphones may be classified as piezoelectric MEMS microphones and capacitive MEMS microphones.
A piezoelectric MEMS microphone includes a vibrating diaphragm, and when the vibrating diaphragm is deformed by external sound, an electrical signal is generated according to a piezoelectric effect to thus measure sound pressure.
A capacitive MEMS microphone includes a fixed electrode and a vibrating diaphragm, and when external sound is applied to the vibrating diaphragm, a space between the fixed electrode and the vibrating diaphragm is changed, thus altering a value of a capacitance. Sound pressure is measured according to the generated electrical signal.
However, most MEMS microphones have a chamber formed by etching on a silicon substrate on one side thereof to allow a sound to pass therethrough, and as the size of an acoustic element is decreased, an area of a vibrating diaphragm is increased against the overall size. In such a structure, if an external impact is applied to a wafer substrate, distortion thereof, or the like, affects residual stress of the vibrating diaphragm itself, and here, stress of the vibrating diaphragm is changed by the external impact to degrade sensitivity of the microphone.
That is, in the related art MEMS microphone, the vibrating diaphragm itself sensing a sound is so thin that it is damaged by a physical external impact in many cases, compared with other condenser-type microphones such as an ECB, or the like.
Matters described in the background art section are provided to promote understanding of the background of the present disclosure, which may include matter that is not prior art known to those skilled in the art to which the present disclosure pertains.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the disclosure and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.